In-process vision detection of flaws and fod by back field illumination

ABSTRACT

A flaw and foreign object debris (FOD) detection system ( 11 ) for use during fabrication of a structure ( 12 ) includes an illumination device ( 13 ). The illumination device ( 13 ) is configured to be in proximity with a fabrication system ( 10 ) and illuminates a portion ( 18 ) of the structure ( 12 ). The illumination device ( 13 ) directs light rays ( 16 ) at acute angles relative to the portion ( 18 ). A detector ( 14 ) monitors the portion ( 18 ) and detects FOD in the portion ( 18 ) during fabrication of the structure ( 12 ) in response to the reflection of the light rays ( 16 ) off of the portion ( 18 ).

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a divisional application of U.S. patentapplication Ser. No. 10/904,719 (filed on Nov. 24, 2004 by Engelbart etal., published on May 25, 2006 under U.S. Pat. Appl. Publ. No.2006/0108048), which is related to U.S. patent application Ser. Nos.10/846,974 (filed on May 14, 2004 by Engelbart et al., published on Feb.3, 2005 under U.S. Pat. Appl. Publ. No. 2005/0025350), Ser. No.10/217,805 (filed on Aug. 13, 2002 by Engelbart et al. and published onFeb. 19, 2004 under U.S. Pat. Publ. No. 2004/0031567), 09/819,922 (filedMar. 28, 2001 and published on Oct. 3, 2002 under U.S. Pat. Appl. Publ.No. 2002/0141632), Ser. Nos. 11/202,411, 11/264,076 and U.S. Pat. No.6,871,684.

TECHNICAL FIELD

The present invention relates generally to the fabrication of compositestructures. More particularly, the present invention relates to systemsand methods of detecting flaws and foreign object debris (FOD) duringthe fabrication of a composite structure.

BACKGROUND OF THE INVENTION

Composite structures have been known in the art for many years. Althoughcomposite structures can be formed in many different manners, oneadvantageous technique for forming composite structures is a fiberplacement or automated collation process. According to conventionalautomated collation techniques, one or more ribbons of compositematerial, known as composite strands or tows, are laid down on asubstrate. The substrate may be a tool or mandrel, but moreconventionally, is formed of one or more underlying layers of compositematerial that have been previously laid down and compacted.

Conventional fiber placement processes in the formation of a partutilize a heat source to assist in the compaction of the plies ofcomposite material at a localized nip point. In particular, the ribbonsor tows of the composite material and the underlying substrate areheated at the nip point to increase resin tack while being subjected tocompressive forces to ensure adhesion to the substrate. To complete thepart, additional strips of composite material can be applied in aside-by-side manner to each layer and can be subjected to localized heatand pressure during the consolidation process.

Unfortunately, defects can occur during the placement of the compositestrips onto the underlying composite structure. Such defects can includetow gaps, overlaps, dropped tows, puckers, and twists. Additionally,foreign objects and debris (FOD), such as resin balls and fuzz balls,can accumulate on a surface of the composite structure. Resin balls aresmall pieces of neat resin that build up on the surfaces of the fiberplacement head as the preimpregnated tows pass through the guides andcutters. The resin balls become dislodged due to the motion andvibration of the fiber placement machine, and drop on to the surface ofthe ply. Subsequent courses of applied layers cover the resin ball and aresultant bump is created in the laminate whereat there may be nocompaction of the tows. The fuzz balls are formed when fibers at theedges of the tows fray and break off as the tows are passed through thecutter assembly. The broken fibers collect in small clumps that fallonto the laminate and are covered by a subsequent layer.

Composite laminates fabricated by fiber placement processes aretypically subjected to a 100 percent ply-by-ply visual inspection forboth defects and FOD. Typically, these inspections are performedmanually during which time the fiber placement machine is stopped andthe process of laying materials halted until the inspection andsubsequent repairs, if any, are completed. In the meantime, thefabrication process has been disadvantageously slowed by the manualinspection process and machine downtime associated therewith.

Current inspection systems are capable of identifying defects in acomposite structure during the fabrication process without requiringmachine stoppage for manual inspections. The inspection systems arecapable of detecting and identifying FOD “in-process” or during thefabrication of a composite structure. This, in turn, eliminates the needfor manual FOD inspections and the machine downtime associatedtherewith.

A split illumination technique has been introduced for the detection offlaws and FOD simultaneously. A first half of a viewing area, referredto as the bright field, is illuminated. A second half of the viewingarea, referred to as the dark field, is not illuminated. The flaws inthe composite structure are detectable within the bright field, but areindistinguishable in the dark field. The FOD is detectable in the darkfield, but is indistinguishable in the bright field. Thus, the splitillumination technique requires the use of dual illumination levels. Theuse of dual illumination levels complicates the inspection process bycausing a single field to be viewed twice, which is time consuming. Asingle field must be viewed twice to inspect for both flaws and FOD.

Thus, there exists a need for an improved system and method of thedetection and identification of flaws and FOD within a compositestructure during the fabrication thereof that simplifies and minimizesthe time involved in the inspection of that composite structure.

SUMMARY OF THE INVENTION

The present invention provides a flaw and foreign object debris (FOD)detection system for use during the fabrication of a structure. Thedetection system includes an illumination device. In one embodiment ofthe present invention, the illumination device is configured to be inproximity with a fabrication system and illuminates a portion of thestructure. The illumination device directs light rays at acute anglesrelative to the portion. A detector monitors the portion and detects FODin the portion during fabrication of the structure in response toreflection of the light rays off of that portion.

In another embodiment of the present invention, the illumination devicedirects light rays, having a single illumination level, at the portionand at acute angles relative to the portion. A detector monitors theportion and detects a flaw and FOD simultaneously in the portion duringfabrication of the structure.

The embodiments of the present invention provide several advantages. Onesuch advantage is the provision of a composite structure in-processfabrication inspection technique that allows for the simultaneousdetection of flaws and FOD for a single field of inspection.

Another advantage provided by an embodiment of the present invention, isthe provision of a composite structure in-process fabrication inspectiontechnique that allows for the simultaneous detection of flaws and FODusing a single illumination level.

Furthermore, the present invention simplifies the composite structureinspection process and minimizes the time involved therein.

Moreover, the present invention allows for the in-process repair of acomposite structure upon detection of a flaw or FOD.

The present invention itself, together with further objects andattendant advantages, will be best understood by reference to thefollowing detailed description, taken in conjunction with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side schematic view of a fabrication system incorporating aflaw and FOD detection system in accordance with an embodiment of thepresent invention;

FIG. 2 is a perspective view of an application portion of a fabricationsystem incorporating a flaw and FOD detection system in accordance withanother embodiment of the present invention;

FIG. 3 is a perspective view of light sources according to theembodiment of FIG. 2;

FIG. 4 is a perspective view of a fabrication system incorporating aflaw and FOD detection system in accordance with another embodiment ofthe present invention;

FIG. 5 is a logic flow diagram illustrating a method of detecting flawsand FOD in a composite structure in accordance with an embodiment of thepresent invention;

FIG. 6 is a side view illustrating low incident angle emission of lightrays for the detection of flaws and FOD in a composite structure inaccordance with an embodiment of the present invention;

FIG. 7 is a front view of a display and user controls illustrating thedetection of flaws and FOD in accordance with an embodiment of thepresent invention; and

FIG. 8 is a logic flow diagram illustrating a method of fabricating acomposite structure in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

In each of the following Figures, the same reference numerals are usedto refer to the same components. While the present invention isdescribed with respect to systems and methods of detecting flaws andforeign object debris (FOD) during the fabrication of a compositestructure, the present invention may be adapted for various applicationsand systems, such as fabrication of structures and components,production line applications, or other applications and systems known inthe art. The present invention may be applied to both the fabrication ofaeronautical and non-aeronautical systems and components.

In the following description, various operating parameters andcomponents are described for one constructed embodiment. These specificparameters and components are included as examples and are not meant tobe limiting.

Also, in the following description the term “foreign object debris(FOD)” refers to any resin ball, fuzz ball, impurity, or other foreignor undesirable object contained within or on a composite structure. FODmay refer to one or more of the stated objects.

In addition, the term “flaw” refers to any defect within a compositestructure or structure under fabrication. A flaw may refer to a tow gap,an overlap of material, a dropped tow, a pucker, a twist or any otherflaw known in the art.

Referring now to FIG. 1, a side schematic view of a fabrication system10 is shown incorporating a flaw and FOD detection and inspection system11 in accordance with an embodiment of the present invention. Thefabrication system 10 includes a lamination system 15, as best seen inFIG. 2, that may utilize an automated collation process to form acomposite structure 12, as shown. The detection system 11 is positionedproximate the composite structure 12 and includes one or moreillumination devices or light sources 13 (only one is shown) and one ormore detectors 14 (only one is shown). The light sources 13 generatelight arrays 16 that are directed at a portion 18 of the compositestructure 12 at low incident angles 20 and at a single illuminationlevel to reveal flaws and FOD 22 simultaneously within that portion 18.A controller 24 is coupled to the detectors 14 and interprets datareceived therefrom, which may be in the form of images. The data may beused to adjust the operation of the fabrication system 10, the detectionsystem 11, and the lamination system 15, and to indicate, detect, andallow for the correction of the flaws and FOD 22. The controller 24 maystore the received data and/or related information in the memory orstorage device 26. System parameters and operation may be adjusted viathe user interface 28.

During the fabrication of the composite structure 12, the compositestructure 12 may be formed of adjacent tows or strips of composite tape(not shown) to form layers 29. The strips include multiple fibers thatare embedded in a resin or other material, which becomes tacky orflowable upon the application of heat. The lamination system 15 arrangesthe strips on a work surface 30 of a table, mandrel, or tool 32, andcompacted with a compaction roller to form the composite structure 12. Acompaction roller 34 can be seen in FIG. 2. The automated collationprocess includes guiding the composite strips from material creels (notshown) to an automated collation or fiber placement machine, such as amachine made by Cincinnati Milacron and Ingersoll Milling Machines. Inparticular, the composite strips are guided to a head unit or assembly36, which may be best seen in FIG. 3, and fed under the compactionroller 34. Focused heat energy is then applied to adhere the incomingmaterial and the underlying previously laid material. With thecombination of pressure and heat, the composite strips are consolidatedinto a previous applied layer to form an additional layer on thecomposite structure 12.

An example of an automated collation technique that may be used isdescribed in U.S. Pat. No. 6,799,619 B2, entitled “Composite MaterialCollation Machine and Associated Method for High Rate Collation ofComposite Materials.” The contents of U.S. Pat. No. 6,799,619 B2 areincorporated herein by reference.

Referring now to the detection system 11, the light sources 13 arepositioned to emit light arrays at the selected portion 18 of thecomposite structure 12. The light sources 13 are positioned at the acuteangles 20 relative to the composite structure 12. In one embodiment ofthe present invention, the acute angles 20 are approximately greaterthan or equal to 2.degree. and are approximately less than or equal to15.degree. Other angles may be used depending on the application. Anynumber of light sources may be utilized even though a specific number isshown.

The light sources 13 are positioned relative to the composite structure12 via a mounting apparatus 40. The mounting apparatus 40 includes amain shaft 42, a secondary shaft 44, and a locking clamp 46 foradjusting the position of the light sources 13. The mounting apparatus40, in turn, can be attached to the frame 48, to the detectors 14, tothe bracket 50, or to some other object that defines a common positionfor both the light sources 13 and the detectors 14 to maintain aconstant spatial relationship relative to one another.

The light sources 13 may be selected from an infrared light or anothertype of light having an infrared component, such as a halogen lightsource or other incandescent light sources. In other embodiments, thelight sources 13 are in the form of a fluorescent light source (e.g.,white light LEDs, a low pressure/mercury filled phosphor glass tube,etc.), a strobe or stroboscopic light source, a noble gas arc lamp(e.g., xenon arc, etc.), a metal arc lamp (e.g., metal halide, etc.), ora laser (e.g., pulsed laser, solid state laser diode array, infrareddiode laser array, etc.). The light from the light sources 13 may passthrough optical fibers to the point of delivery, an example of which isshown in FIG. 4. The light sources 13 may include LEDs arranged in anarray or cluster formation. In one specific embodiment, the lightsources 13 include twenty-four LEDs mounted in an array upon athree-inch square printed circuit board.

In some embodiments, the light sources 13 are operated at a power levelthat increases the infrared (IR) component of the light arrays, whichaids in the inspection of dark tow material, such as carbon. In thisregard, exemplary power levels in the range of approximately one hundredfifty watts (150 W) and in the wavelength range of about seven hundrednanometers to one thousand nanometers (700 nm-1000 nm) may be used.However, the particular power levels and wavelengths for the lightsources 13 depends at least in part on the speed and sensitivity of thedetectors 14, the speed at which the material is being laid, the lightdelivery losses, and the reflectivity of the material being inspected.

The detectors 14 may be of various types and styles. A wide range ofdetectors may be used including commercially available cameras capableof acquiring black and white images. In one embodiment, the detectors 14are in the form of a television or other type of video camera having animage sensor (not shown) and a lens 13 through which light passes whenthe cameras are in operation. Other types of cameras or image sensorscan also be used, such as an infrared-sensitive camera, a visible lightcamera with infrared-pass filtration, a fiber optic camera, a coaxialcamera, a charge coupled device (CCD), or a complementary metal oxidesensor (CMOS). The detectors 14 may be positioned proximate thecomposite structure 12 on a stand (not shown) or mounted to the frame 48or a similar device. In embodiments of the present invention that do notinclude a reflective surface, the detectors 14 may be positionedapproximately six inches from the top surface 52 of the compositestructure 12, and mounted to the frame 48 by way of the bracket 50 andassociated connectors 54. Also, any number of detectors may be utilized.

The controller 24 may be microprocessor based such as a computer havinga central processing unit, memory (RAM and/or ROM), and associated inputand output buses. The controller 24 may be a portion of a central maincontrol unit, be divided into multiple controllers, or be a singlestand-alone controller as shown.

The connectors 54 may be rivets, screws, or the like and used to mountthe detectors 14 to the frame 48 in a stationary position.Alternatively, the connectors 54 may be a hinge-type connector thatpermits the light sources 13, the detectors 14, and associated assemblyto be rotated away from the composite structure 12. This embodiment isadvantageous in situations when there is a desire to access parts of thematerial placement device that are located behind the detectors 14 andassociated assembly, such as during maintenance, cleaning, or the like.

The detection system 11 may also include filters 56 (only one is shown),which may be utilized in conjunction with the lens 58 for filtering thelight passing therethrough. In one embodiment, the filters 56 aredesigned to filter the light such that the infrared component of or acertain infrared wavelength or range of wavelengths of the light is ableto pass into the detectors 14. Thus, the filters 56 may prevent ambientvisible light from entering the detectors 14 and altering the appearanceof the captured image.

Other methods of filtering light can also be used to achieve the same,or at least used to provide a similar result. For example, the detectors14 may be designed to include a built-in filter of equivalent opticalcharacteristics. In addition, the filter 56 may be located between thelens 58 and the detectors 14. Alternatively, the detectors 14 mayinclude image sensors that are sensitive in the infrared spectrum (i.e.,an infrared-sensitive camera), thus eliminating the need for the filters56.

The detection system 11 may also include a marking device 60 for markingthe location of the defects and the FOD on the composite structure 12.The marking device 60 may be attached to the frame 48 and be triggeredby the controller 24 or similar device when a flaw or FOD is detected.The marking device 60 may deposit ink, paint, or the like onto thecomposite structure 12 in areas where flaws and FOD have been detected.The markings on the composite structure 12 enable the location of theflaws and FOD to be subsequently and readily identified eitherautomatically or manually. The marking device 60 may also be adapted tomark flaws with different colored ink than that used to mark FOD.Alternatively, other marking or indicating methods can also be used,such as markings utilizing a pump-fed felt-tip marker or a spring-loadedmarking pen, indications via audio or visual alerts, and the like.

Referring now to FIGS. 2 and 3, a perspective view of an applicationportion of a fabrication system 10′ incorporating a flaw and FODdetection system 11′ and a perspective view of light sources 13′ areshown in accordance with another embodiment of the present invention.The detection system 11′ includes two light sources 13′ (only one isshown) positioned relative to the composite structure 12 and thecompaction roller 34 on either side of a reflective surface 70 and adetector 14′. FIG. 2 illustrates an alternative embodiment of thehinge-type connector 54 that mounts the light sources 13′, the detector14′, the reflective surface 70, and associated head assembly 36 to theframe 48 by way of the bracket 50.

The light sources 13 and 13′ and the detectors 14 and 14′, of FIGS. 1and 2, may be translated or moved relative to a composite structure,such as the composite structure 12. The adjustability and moveability ofthe light sources 13 and 13′ and detectors 14 and 14′ providesflexibility in the capture of images of a composite structure. Samplesystems including moveable cameras and light sources are described indetail in previously referred to U.S. patent application Ser. No.10/217,805.

Although the light sources 13′ are shown in the form of four halogenlight bulbs 74, other quantities, types, and styles of illuminationsources may be utilized. A light reflection element 76 is located nearthe light sources 13′. The reflection element 76 includes a series oflight reflecting surfaces 78 that redirect the light towards the desiredarea to be illuminated. This levels the illumination across the topsurface of a composite structure and eliminates, or at leastsubstantially reduces, the areas of intense light (i.e., hotspots)created by the brightest portion of the light source. Hotspots can leadto errors during the processing of images. The light reflection elements78 are particularly advantageous for illuminating the curved/contouredsurfaces of the composite structures because the redirection of thelight permits a larger portion of a composite structure to be evenlyilluminated.

The reflection element 76 is curved around the light sources 13′, suchas in a parabolic shape. The reflection elements 78 are in the form ofcurved steps that are substantially parallel to the light source 13′.The distance between and the curvature of the reflection elements 78 maybe selected for sufficient and even illumination generated from the sumof the two light sources 13′. This enables more consistent illuminationof the composite structure 12, which prevents, or at least reduces, theimage-processing errors due to inconsistent illumination of thecomposite structure 12. Alternatively, the shape and/or surfaceconfiguration of the reflection elements 78 may be modified using othertechniques known in the art to produce consistent illumination andscattering of light.

In an exemplary embodiment, seventeen reflection elements are utilizedand have an overall parabolic shape and a range of widths from about0.125 inches at the outer edge of the reflection elements to about 0.250inches at the center of the reflection elements. The reflection elementsalso have a uniform step height of about 0.116 inches. In otherembodiments, however, the reflection elements 78 may be provided withdifferent numbers of steps having different uniform or varying widthsand different uniform or varying step heights.

Furthermore, the reflection elements 78 may be adjusted in order todirect the light produced by the light sources 13′ and scattered by thereflection elements 78 toward the selected portion of a compositestructure. For example, as shown in FIG. 3, the reflection elements 78are mounted to the mounting apparatus 40 with fasteners 80. Thefasteners 80, when loose, are capable of being slid within slots 82 tocorrespondingly adjust the angle of the reflection elements 78 relativeto a composite structure. Once the reflection elements 78 are positionedappropriately, the fasteners 80 are tightened to secure the reflectionelements 78 in the desired position. Adjustments of the reflectionelements 78 can also be enabled by other methods, such as by electronicmeans that permit remote adjustment of the reflection elements 78.

The detectors 14 are positioned near the composite structure 12 and whenin the form of cameras are positioned to capture images of the selectedilluminated portion, which is typically immediately downstream of thenip point at which a composite tow is joined with the underlyingstructure.

The light sources 13, the detectors 14, the reflective surface 16, andany reflection elements 78, may be mounted on the head unit 23 to allowfor continuous capture of real-time data of the composite structure 12.The real time data may be captured as the head unit 36 is transitionedacross the composite structure 12 and as the composite strips are laiddown or applied.

The bracket 50 may be fastened to the hinge type connector 54 via asuitable fastener, such as a thumbscrew or any other fastener that maybe utilized and inserted through hole 72 and then tightened to securethe assembly in place for operation. The fastener may be loosened orremoved, for example, to rotate the light source and detector assemblyaway from the compaction roller 34 and other parts of the fabricationsystem.

The reflective surface 70 may be positioned near the composite structure12, and angled such that the reflective surface 70 reflects an image ofthe illuminated portion to the detectors 14. In one embodiment, theangle of the reflective surface 70 to the composite structure is aboutsixty-five degrees, but the reflective surface 16 can also be positionedat any appropriate angle in order to reflect images of the illuminatedportion to the detectors 14. The detectors 14 may be positioned to pointtoward the reflective surface 70 in order to capture the close-rangeimages of the illuminated portion from the reflective surface 70. Morethan one reflective surface 70 may also be utilized in furtherembodiments of the present invention in which the reflective surface 70cooperate in order to direct the images of the illuminated portion tothe detectors 14.

The reflective surface 70 may be in various positions relative to aselected portion, such as portion 18. Reflective surface 70 can also beutilized to allow the detectors 14 to be placed in an advantageouspositions, which might otherwise be blocked by portions of thecompaction roller 34 and/or other parts of the fabrication system.

The configuration illustrated in FIG. 2 aids in the capturing of imagesof curved/contoured surfaces of a composite structure since thereflective surface 70 is positioned close to the composite structure. Inaddition, this configuration permits the detectors 14 to be positionedaway from a composite structure, to prevent interference between thedetectors 14 and components of the fabrication system 11′. Further, thereflective surface 70 can also provide a “square on” view of theselected portion being inspected, which, in turn, can improve theability to dimension the two gaps for pass/fail decisions.

Referring now to FIG. 4, a perspective view of a fabrication system 10″incorporating a flaw and FOD detection system 11″ in accordance withanother embodiment of the present invention is shown. The detectionsystem 11″ includes lights sources (not shown) that are at a remotelocation. The light sources generate light rays, which are passedthrough linear optical fiber arrays or fiber optic cable 90 to point oftransmission 92 via light emitting heads 94. Light arrays are emittedfrom the fiber optic cable 90 toward the selected portion 18′ of thecomposite structure 12′ to detect flaws and FOD 22′. The use of fiberoptic cables simplifies the number of components mounted on the headassembly.

Referring now to FIGS. 5 and 6, a logic flow diagram illustrating amethod of detecting flaws and FOD in a composite structure and a sideview illustrating low incident angle emission of light rays for thedetection of flaws and FOD in a composite structure are shown inaccordance with an embodiment of the present invention.

In step 100, a portion 18″ of concern of a composite structure 12″ isselected. The portion 18″ may include a segment or area of or mayinclude the entire composite structure 12″. In step 102, the lightsources 13″ are activated to illuminate the selected portion 18″, whichmay include as stated selected areas of or the entire compositestructure 12″. The light rays 96, which may be in the form of arrays,are generated at a single illumination level. The illumination level issuch that both flaws and FOD 22″ may be detected simultaneously withinthe selected portion 18″. The light source 13″ may be activatedthroughout the material placement process.

In step 104, the light rays 96 are directed at the portion 18″ and atlow incident or acute angles 20′ relative to the portion 18″. Lowincident lighting allows foreign objects to be easily distinguishablefrom a background of the laminate or the composite structure 12″ onwhich material is being placed. As the composite structure 12″ isilluminated, light is directed toward the edges of any FOD, such as FOD97. This illumination allows for the shape and size of the FOD to bedetected and is referred to as “backfield illumination”. The lowincident illumination also creates a shadow within flaw areas, such aswithin a gap, such as gap 98. In one example embodiment, the angles ofthe light arrays relative to the composite structure 12″ areapproximately greater than or equal to 2.degree. and less than or equalto 15.degree. The angles of the light arrays may be adjusted dependingupon the conditions to provide desired image quality.

In step 106, detectors, such as detectors 14 and 14′, monitor theportion 18″ and generate status signals in response to the reflection ofthe light rays 96 off of the portion 18″. The status signals containinformation regarding the existence of flaws and FOD in the portion 18″.The detectors 14 and 14′ detect light reflection characteristics of theFOD. The contrast between the shadow and the composite structure isdetected and thus allows for the detection of flaws or FOD. The flaw andthe FOD 22″ are thus detected simultaneously for the same illuminationportion, in this example, portion 18″. This allows for smaller areas ofa structure to be examined at any single time. The detectors may detectflaws and FOD during the fabrication of the composite structure 12″.

In step 108, the detected flaws and FOD 22″ are indicated to a user viaa display, such as that shown with respect to FIG. 7.

Referring now to FIG. 7, a front view of a user display screen 120 anduser controls 122 illustrating the detection of flaws and FOD 124 inaccordance with an embodiment of the present invention is shown.Although the operation and use of the display 120 is primarily describedwith respect to the embodiment of FIG. 1, it may be easily modified forand applied to other embodiments of the present invention. The userinterface 28 includes the display 120, such as that on a computermonitor, and can also include an input device, such as a keyboard andmouse (not shown), for permitting an operator to move a cursor about thedisplay 120 and input various system settings and parameters. Thedisplay 120 may be touch-sensitive for permitting the operator to inputthe desired settings by manually touching regions of the display screen.

The interface 28 includes a window 126 in which an image 128, of thecomposite structure 12, is displayed for viewing by an operator or otheruser. The image 128 may be in the form of an unprocessed or processedcamera image. When processed the image 128 or a portion thereof may bebinarized. During binarization, all shades of gray above a predeterminedthreshold value may be changed to white, while all gray shades below thethreshold value may be changed to black to heighten the contrast ofdefects and improve the accuracy of defect detection. As an alternativeor in addition to binarization, rates of light level change in the rawimage and color changes in the images may be used to identify thedefects and FOD.

The controls 122 allow for various user inputs to the system. Thecontrols 122 may be used to adjust the binarization threshold.Generally, the setting of the binarization threshold involves a tradeoffbetween the sensitivity with which defects are detected and theresolution with which the defects are depicted. In one embodiment, thebinarization threshold is set to about 128, which corresponds to themid-point on the 8-bit digitizing range of 0 to 255. However, otherbinarization threshold values may be employed depending at least in parton the particular application, available lighting, camera settings, andother factors known in the art.

The controls 122 also allow the user to adjust or shift the viewing areawithin the window 126. During operation, the window 126 displaysreal-time moving video images of the illuminated portion of thecomposite structure 12 as the detectors 14 and/or the reflective surface18 are moved relative to the composite structure 12. The controls 122may be such to allow the user to input the maximum allowable dimensionalparameters, the acceptable tolerances, as well as other known parametersfor the flaws and FOD.

In addition to displaying images of the composite structure 12, thedisplay screen 80 may also include a defect table 128, which lists thediscovered flaws and FOD and provides related information thereof, suchas location, size, and the like. The display 120 can further includestatus indicators 130 that notify the user whether a particular imagearea is acceptable or not acceptable based on predefined criteria, suchas the maximum allowable dimensional parameters and tolerances.

Referring now to FIG. 8, a logic flow diagram illustrating a method offabricating a composite structure in accordance with an embodiment ofthe present invention is shown. Although the logic flow diagram of FIG.8 is primarily described with respect to the embodiment of FIG. 1, itmay be easily modified to apply to other embodiments of the presentinvention.

In step 150, the fabrication system 10 applies the strips to form thelayers 29 on the substrate 32 to form the composite structure 12. Instep 152, the detection system illuminates selected portions of thecomposite structure 12 during the application of the strips to detectthe flaws and FOD 22 as described above with respect to the method ofFIG. 5.

In step 154, the detection system 11 distinguishes and identifies theflaws and FOD 22 and the location thereof and generates a compositestructure defect signal. Examples regarding systems and methods foridentifying defects in a composite structure during fabrication thereofare included in U.S. patent application Ser. No. 09/819,922, filed onMar. 28, 2001, entitled “System and Method for Identifying Defects in aComposite Structure” and in U.S. patent application Ser. No. 10/217,805,filed on Aug. 13, 2002, entitled “System for Identifying Defects in aComposite Structure”. The contents of U.S. patent application Ser. Nos.09/819,922 and 10/217,805 are incorporated herein by reference as iffully set forth herein.

In step 156, the fabrication system 10 may in response to the compositestructure defect signal alter the operation thereof. The fabricationsystem 10 may cease further application of the strips until one or moreportions of the composite structure 12 are repaired, may alter themanner in which the strips are applied, may adjust parameters of thefabrication system 10 or detection system 11, or may perform other tasksknown in the art.

At any time upon or after the generation of the status signals and/orthe defect signals the controller 24 may store data or images in thestorage device 26 for future analysis and/or processing.

The above-described steps in the methods of FIGS. 5 and 8, are meant tobe illustrative examples, the steps may be performed synchronously,continuously, or in a different order depending upon the application.

The present invention provides systems and methods for the simultaneousdetection of flaws and FOD using a single illumination level. Thepresent invention simplifies the detection of the flaws and FOD andallows for efficient identification and repair thereof.

While the invention has been described in connection with one or moreembodiments, it is to be understood that the specific mechanisms andtechniques which have been described are merely illustrative of theprinciples of the invention, numerous modifications may be made to themethods and apparatus described without departing from the spirit andscope of the invention as defined by the appended claims.

1. A fabrication system comprising: a lamination system comprising alayer applicator applying a plurality of composite material layers to asubstrate to form a structure; and a flaw and foreign object debris(FOD) detection system proximate said lamination system comprising; atleast one illumination device illuminating a portion of the structure,said at least one illumination device directing light rays at saidportion and at acute angles relative to said portion; and at least onedetector monitoring said portion and detecting FOD in said portionduring application of said plurality of composite material layers inresponse to reflection of said light rays off of said portion.
 2. Afabrication system as in claim 1 further comprising an indicatorindicating detection of said FOD.
 3. A fabrication system as in claim 2wherein said indicator comprises a processor.
 4. A fabrication system asin claim 1 wherein said lamination system adjusts operation of saidlamination system in response to said detection.
 5. A fabrication systemas in claim 1 wherein said lamination system delays further applicationof said plurality of composite material layers in response to saiddetection for repair of said portion.
 6. A fabrication systemcomprising: a lamination system comprising a layer applicator applying aplurality of composite material layers to a substrate to form astructure; and a flaw and foreign object debris (FOD) detection systemproximate said lamination system comprising; at least one illuminationdevice illuminating a portion of the structure, said at least oneillumination device directing light rays having a single illuminationlevel at said portion and at acute angles relative to said portion; andat least one detector monitoring said portion and detecting at least oneflaw and FOD simultaneously in said portion during application of saidplurality of composite material layers in response to reflection of saidlight rays off of said portion.
 7. A fabrication system as in claim 6further comprising an indicator indicating said at least one flaw orsaid FOD.
 8. A fabrication system as in claim 7 wherein said indicatorcomprises a processor.
 9. A fabrication system as in claim 6 whereinsaid lamination system adjusts operation of said lamination system inresponse to said detection.
 10. A fabrication system as in claim 6wherein said lamination system delays further application of saidplurality of composite material layers in response to said detection forrepair of said portion.
 11. A fabrication system as in claim 1, whereinsaid flaw and foreign object debris (FOD) detection system furthercomprises at least one controller coupled to said at least one detectorfor receiving and interpreting information received therefrom for use inadjusting the fabrication system whereby the flaw and the FODs can becorrected.
 12. A fabrication system as in claim 11, wherein said acuteangles are approximately greater than or equal to 2° and approximatelyless than or equal to 15° relative to said portion.
 13. A fabricationsystem as in claim 1, wherein said at least one detector detects atleast one flaw and said FOD.
 14. A fabrication system as in claim 1,wherein said at least one detector detects contrast differences betweensaid FOD and said portion.
 15. A fabrication system as in claim 1,wherein said at least one illumination device comprises: a firstillumination device directing a first set of light arrays at saidportion; and a second illumination device directing a second set oflight arrays at said portion.
 16. A fabrication system as in claim 1,wherein said at least one detector generates a status signal in responseto said detection.
 17. A fabrication system as in claim 1, wherein saidat least one illumination device is selected from at least one of anincandescent light, a light emitting diode, a noble gas arc lamp, ametal arc lamp, a strobe, a fluorescent light, an infrared light, and alaser.
 18. A fabrication system as in claim 1, wherein said at least onedetector is selected from at least one of a camera, an infrared sensor,a visible light sensor, a visible light sensor with infrared passfiltration, and a charged-coupled device.
 19. A fabrication system as inclaim 6, wherein said flaw and foreign object debris (FOD) detectionsystem further comprises at least one controller coupled to said atleast one detector for receiving and interpreting information receivedtherefrom for use in adjusting the fabrication system whereby the flawand the FODs can be corrected.
 20. A fabrication system as in claim 19,wherein said acute angles are approximately greater than or equal to 2°and approximately less than or equal to 15° relative to said portion.21. A fabrication system as in claim 6, wherein said at least onedetector detects contrast differences between said FOD and said portion.22. A fabrication system as in claim 6, wherein said at least oneillumination device comprises: a first illumination device directing afirst set of light arrays at said portion; and a second illuminationdevice directing a second set of light arrays at said portion.
 23. Afabrication system as in claim 6, wherein said at least one detectorgenerates a status signal in response to said detection.
 24. Afabrication system as in claim 6, wherein said at least one illuminationdevice is selected from at least one of an incandescent light, a lightemitting diode, a noble gas arc lamp, a metal arc lamp, a strobe, afluorescent light, an infrared light, and a laser.
 25. A fabricationsystem as in claim 6, wherein said at least one detector is selectedfrom at least one of a camera, an infrared sensor, a visible lightsensor, a visible light sensor with infrared pass filtration, and acharged-coupled device.